How To Plumb An Island Sink

How To Plumb An Island Sink

It’s little wonder that you’ve been dreaming about an island sink for years. Kitchen islands are among the most coveted of kitchen features, and a sink can make your island just that much more desirable. Plumbing an island sink isn’t much more complicated than plumbing a standard sink, with just one exception. The drainage for an island sink must be installed in a special configuration, or a special vent called an “air admittance valve” must be installed on the drainage pipe. This step-by-step tutorial will walk you through the process of installing the plumbing for an island sink using an air admittance valve.


  • Plumber’s wrench
  • Pipe cutter
  • Multiple types of pipes and fittings, depending on the configuration of your kitchen and plumbing
  • Materials for attaching pipes, like a soldering iron or PVC glue. (The exact materials will depend on the type of pipes you’re working with)


  1. Turn off the water supply to the kitchen using the local shut off valves, or cut off the water supply to the house. You may need a plumber’s wrench to turn off the water to your house, if the shut off valve is difficult to turn.
  2. Use a pipe cutter to cut into the existing cold and hot water lines, and the drain. Remove a small section of pipe from each plumbing line.
  3. Install a T-fitting into each hot and cold water pipe, pointing the post of the T in the direction of the location where the island sink will be. Install a Y-fitting into the drain line, pointing the fitting in the general direction of the island sink. If you’re soldering together copper piping for this project, take a look at this video for more instructions. If you’re connecting two PVC pipes, watch this video for instructions.
  4. Install the water supply lines for the sink faucet to the existing hot and cold water lines, running the pipes to the area where the faucet will be located. Run a drain line from the area beneath the sink in the island to the main drain line where you just installed the Y-fitting.
  5. Install a sanitary T-fitting to the drain pipe in the area beneath the island sink, and attach shut off valves to the hot and cold water supply lines in the area just beneath the sink.
  6. Attach an air admittance valve to the top of the sanitary T-fitting attachment you installed in Step 5.
  7. Attach the tail piece to the bottom of the sink basket in the drain.
  8. Attach the P-trap to the tail piece, then connect the P-trap to the opening in the T-fitting on the drain pipe.
  9. Screw the cold and hot water hookups to the cold and hot water supply lines beneath the sink.

With all this done, you can turn on the water once again. Check all connections for leaks and make adjustments as necessary. Now your sink is ready to go.

You can watch this entire process here.

Of course, not everyone wants to plumb their own island sink. If you’re not up for this, and you’re a resident of the Pittsburgh area, you’re in luck! Terry’s Plumbing is happy to make this installation for you. Contact us today for more information.

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